Impulse electric clock



March 24, 1953 A. AMEND, JR

IMPULSE ELECTRIC CLOCK 3 Sheets-Sheet 1 Filed Feb. 16, 1949 iNSULRTlONJ1me Np, \IR.

March 24, 1953 AMEND, JR

IMPULSE ELECTRIC CLOCK 3 Sheets-Sheet 2 Filed Feb. 16, 1949 NYENTOQDOLPH MEND JR. .5 QfiTTORNEZY March 24, 1953 AMEND, JR

IMPULSE ELECTRIC CLOCK 3 Sheets-Sheet 3 Filed Feb. 16, 1949 w w m wBayard-for Q A D m MI w W. nwb

Patented Mar. 24, 1953 UNITED STATES PATENT QFFICE IMPULSE ELECTRICCLOCK Adolph Amend, J r., Harrison Park, N. J assignor to General TimeCorporation, a corporation of Delaware Application February 16, 1949,Serial No. 76,706

vide an electricclock for battery operation which is inherently of highaccuracy in spite of wide variations in battery voltage. It is anotherobject to provide an impulse clock which is extremely durable andcapable of maintaining accuracy over long periods of time in spite ofthe shock and vibration encountered. in automotive use. It is a furtherobject related. to the above to provide an electric clock which is notonly compact but of simple and straightforward construction enabling themanufacturing cost to be reduced to a minimum, an important feature in ahighly competitive field where profit margins are small. A more detailedobject is to provide a clock which is inherently efiicient, the batterydrain being sufliciently low as to enable it to run for long periodswithout battery recharge or replacement, thus making possible accuratetime keeping remote from a commercial alternating current supply.Although electrical contacts are 7 used, interference with nearby radiosets is nonexistent.

Other objects and advantages of the invention will be apparent from thefollowing detailed description taken in connection with the accompanyingdrawings, in which:

Figure 1 is a side view in elevation of a clock constructed inaccordance with the present invention.

Fig. 2 is a sectional view taken along line 2-2 of Fig. 1, the clockbeing viewed from the rear.

Fig. 3 is a horizontal section looking downwardly along the section line3-3 of Fig. 2.

Fig. 4 is a perspective view of the armature assembly with a portionthereof broken away to show the contact structure in greater detail.

Fig. 5 is a perspective view similar to Fig. 4 showing the other side ofthe armature assembly.

Fig. 6 is a fragment showing the combined balance wheel, hairspring, andcontacts operated thereby.

Figs. 7-11 are stop motion views showing the positions of the armatureand contacts as well as the direction of movement of the balance wheelat the various periods in the operating cycle.

Fig. 12 sets forth the wiring diagram in more or less schematic form.

While the invention is susceptible of various modifications andalternative constructions and uses, I have shown in the drawings andwill here 4 Claims. (CI. 58-28) I vention.

alternative constructions and uses falling within the spirit and scopeof the invention as expressed in the appended claims.

Referring now to the figures, and particularly Figs. 1-3, a clock 29 isshown having a frame which includes mounting plates 2|, 22 and; 23spaced from one another in parallel relation by posts 24. The clock face26 is arranged parallel to the plate 23 and the time is indicatedthereon by a set of hands 21. As is conventional, the hands are drivenby means of a gear train indicated generally at 28. The initial gear 29of the series is driven by a worm 32 mounted on the plate 22. Thepresent invention is concerned with an improved mechanism for causingthe gear train to be accurately driven and in the present instance forcausing rotation of the worm 36.

To this end a timing mechanism is employed which comprises an armatureassembly indicated generally at 34 (see Figs. 4 and 5) which is actuatedperiodically by means of an electromagnet 35. Prior to discussing thearmature assemblyit will be helpful to inspect the manner in which theelectromagnet 35 is constructed and mounted. As shown to best advantagein Fig. 2 it includes a C-shaped pole piece 36 having legs 31, 38. Theselegs are opposite one another and have faces arcuately formed to receivethe armature assembly 34 between them. The' faces include raisedprojections or teeth 39 which serve to concentrate the magnetism and topull similarly shaped teeth on a cooperating armature into alinement.Encircling the centerportion of the electromagnet 35 is a coil 4-9having many turns of fine wire wound thereon. For a purpose which willlater appear, a short-circuiting sleeve of copper 46 surrounds the coreand is included within the coil it.

Turning attention now to the armature assembly shown in Figs. 4 and 5 itwill be noted that it includes a pair of supporting plates 45, 46 havinga plate-like magnetic armature 4'! supported between them on posts 48,4.9. The plates 45, 4B are preferably insulated from one another, forexample by insulating washers 5B for the purpose of conducting currentto the contacts which are internally contained. The ends of the armature57 are preferably made convex and include toothed projections 54 formating with the projections 39 previously referred to.

In order to support the armature assembly 34 within the frame of theclock, the supporting plates 45; 46 are provided with axially extendingtrunnions or spindles 55, 56. As shown in detail in Fig. 3 such spindlesare respectively received in apertures provided in the plates 2!, 22.

In practicing-the invention in one of its aspects means are provided fornot only making an electrical connection with the respective supportingplates 45, 46 but for biasing the armature assembly 34 as a whole to abacked-off o1- deenergized position in which it is cocked at a smallangle with respect to the pole pieces N, 38 of the electromagnet. In thepresent instance thi is accomplished by hairsprings El, 58 which areconnected at their inner ends to the respective spindles 55, E. Theouter ends of the hairsprings are anchored to the frame by terminals 59,ee supported on plates 2|, 22. In order to insulate these terminals fromone another the plate is formed of insulating material such as plasticand includes a terminal plate Zia riveted or. otherwise-fastened theretofor both receiving the spindie. 55. and for mounting the terminal 55.With thearmature assembly mounted as shown it will be apparent that itand the associated hairsprings arecompletely shielded. Protectionagainst dam age is insured by the fact that the structure is equivalentto one rigid box rotating through a limited are inside another box.Further, the

I assembly 34 as a whole may be readily balanced about its axis ofrotation so that shocks and vibration will affect all parts of theassembly equally and there will be no net rotation effect to interferewith the magnetically-produced rocking movement.

Included within the armature assembly 3% and mounted for rotation withrespect thereto is a balance wheel 64 having a shaft 65. The ends of theshaft 65 are respectively received in jeweled or similar low-frictionbearings 85, $1, the latter bearing being preferably axially adjustable.

Mounted adjacent the balance wheel Kit is a hairspring 68 having itsinner end connected to the shaft 65 of the balance wheel and serving totransmit torque thereto in one direction 'or the other. The outer end ofthe hairspring 68 carries an enlargement 14 which is flexibly mountedand which is constrained so that it may undergo only a limited amount ofmovement in either direction. Movement in one direction, clockwise asviewed in Fig. 6 and counterclockwise as viewed in Fig. 4, is preventedby means of a stop l5 affixed to the armature plate ll. the oppositedirection is strictly limited by means of, astop consisting of a contactit which passes through an aperture l! in the armature plate and whichissecurely supported on the insulated plate (Fig. 4). It will be seen,therefore, that the outer end of the hairspring is constrained to movein general with the armature assembly rec ognizing, of course, that thestops allow a very limited amount of lost motion. Consequently,

rocking movement of the armature assembly Movement in pulse to the outerend of the hairspring, and thence to the balance wheel, in eitherdirection. In the embodiment disclosed the impulse produced by movementof the armature into the energized position tends to wind the springmore tightly While rocking into the deenergized position under theinfluence of the return spring tends to unwind the hail-spring. It willbecome apparent as the discussion proceeds that the direction of thespiraling and hence the direction of winding or unwinding could bereversed from that shown without in any way departing from the presentteachings. It may further be noted that the balance wheel is coaxialwith the mounting of the armature assembly as a Whole. This has a numberof beneficial effects worthy of mention. First of all it reduces to aminimum the rotational inertia of the assembly es, increasing therapidity of rocking in response to external magnetism and spring forces.This is particularly important where the principle is adopted to largerclocks having heavier balance wheels. In addition it facilitates staticbalancing of the assembly previously alluded to and insures that theimpulse force is of maximum value, being applied exactly tangentially tothe outer end of the hairspring.

In accordance with the present invention tension in the h-ai'rs'p'ring6-8 associated with the balance wheel and the consequent movement of theouter end portion of the hairspring is caused to actuate a pair ofelectrical contacts to produce energization of the electromagnet. In thepresent instance the contacts include the relatively i'ixed contact Itas well as a cooperating movable contact I la which is mounted on theenlargement 74 connected to the hairspring. In practicing the inventionmeans are further provided normally biasing the contacts 16, Ma into theopen position so that closure of the contacts takes place only after apredetermined reactive force has been built up in the hairspring 68. Inthe present instance such biasing is accomplished by means of a leafspring 18 which is rigidly anchored within the armature assembly bymeans of a supponting post 19. The outer or movable end of the spring 78is fixed to the enlargement M and hence to the movable contact Ma. byriveting or any other desired means. Because of the action of thebiasing spring 18 the contacts l6, lea will be in. the open positionwhen the balance wheel and hairspring are at rest. The biasing force ofthe spring l8, however, is made sufiicien-tly weak so that it is readilyovercome and the contacts thus allowed to close upon rotation of thebalance wheel in the close direction. The latter direction is justopposite to the direction of rocking of the armature when theelectromagnetic is energized. The force on the movable contact Ma as aresult of balance wheel travel and the force on the relatively fixedcontact 1.6 as a result of armature energization thus 1 add together toinsure a good electric-a1 connec- With the contacts and associated partsin the armature assembly arranged as shown, the electromagnet will beenergized cyclically to cause cyclic oscillation of the armature with aperiod which is dependent upon the natural period of the balance wheel64 and its associated hairspring 68. lit is particularly important tonote that the balance wheel is freely rotating and that the only torquetransmitting connection thereto is the inner end of the hairspring 6%.Escapements are entirely eliminated and the only work which must be doneby the balance wheel is the overcoming of bearing friction and windage.Assuming that low-friction bearings are used, the periodicity will becompletely unaffected by the frictional forces which may develop inother portions of the mechanism. It might be thought that the movementof the contact 14a at the end of the hairspring would cause power to bedrawn from the hairspring and associated balance wheel. While this maybe true over a very small portion of the cycle it is to be particularlynoted that whatever energy is thus subtracted is resiliently stored andis thus completely returned to the balance wheel and hairspring during asucceeding portion of the cycle.

The operation of the device as thus far described will be made clearupon inspection of the stop motion views shown in Figs. 7-11. Thecontacts are initially open by reason of the biasing spring 18;consequently the armature 41 is in its upwardly tilted or deenergizedposition. It will be assumed in order to start the cycle that acounterclockwise impulse is applied directly to the balance wheel asindicated by the arrow. Upon appreciable rotation of the balance wheelin such direction, the hairspring 68 will be increasingly wound andeventually the force at its outer end will be suflicient to deflect thebiasing leaf spring 18 so that the contacts 16, Ma are closed. Thiscondition is shown in Fig. 8. The

latter contacts are arranged in series with the coil 40 of theelectromagnet so that the electromagnet becomes energized. This ofcourse results in the overcoming of the force of the arm-ature returnsprings 51, 58 and the rotation of the armature 41 in a clockwisedirection. Under this condition as shown in Fig. 9 the teeth on thearmature and pole pieces are seen to be in alinement.

The coil and associated magnetic circuit are preferably designed so thatthe rotation of the armature into its energized position takes placealmost instantaneously. There will, of course, be some small delaybecause of the build-up of magnetic flux but such delay is on the orderof a very small fraction of a second and from a practical standpoint isnegligible in view of the inertia of the balance wheel. The suddentangential movement cf the outer end of the hairspring immediatelyproduces a torque impulse on the balance wheel. Assuming that the spring78 is of proper stiffness readily determined by one skilled in the art,such impulse will occur at about the time that the balance wheel isdecelerating toward a stop in the counterclockwise direction withconsiderable energy stored in the wound hairspring. The impulse,occurring at this time, aids reversal of the balance wheel, as thebalance wheel is caused to rotate in a clockwise direction as shown inFig. 10 under the urging of the hairspring. As an incident to suchmovement the stress in the hairspring will decrease to a point where itis overcome by th biasing force of the spring 18 thus causing thecontacts to open.

The final portion of the cycle is disclosed in Fig. 11. Opening of thecontacts has allowed the armature A! to return to its upwardly rocked ordeenergized position. This applies a return impulse to the outer end ofthe hairspring. At the same time, continued rotation of the balancewheel has caused it gradually to decelerate and the kinetic energy ofthe balance wheel to be stored in the unwound hairspring. As a result.rotation in a clockwise direction ceases and, as indicated by thedotted arrow, reversal takes place, the balance wheel being impelled ina counterclockwise direction by the energy stored in the spring. This,it will be recalled, places the mechanism in the same direction asdisclosed in Fig. 7 and the cycle is repeated as long as impulsingvoltage is available.

In practicing the present invention, the successive timed oscillationsof the armature assembly 34 are caused to drive the gear train 28 andthe indicating hands 2?. To accomplish this a ratchet wheel 8!) which iscoupled to a worm 30 (Fig. 2) is rotatably mounted on the opposite sideof plate 22 from the armature assembly. A portion of the teeth ofratchet wheel to projects through a slot in plate 22. Retrogrademovement of the ratchet wheel is prevented by means of pawl 8i. Totransmit force from the armature assembly to the ratchet wheel, a pawlin the form of a light leaf spring 82 is employed.

This spring is preferably arcuately shaped, being anchored to thearmature assembly at one end and having a free end 83 which bearslightly against the face of plate 22. As the armature rotates under theinfluence of the electromagnet, the leading edge of the spring 82 iscaused to bear against the ratchet wheel advancing the same at the rateof one tooth per cycle.

It should be noted that preferably the ratchet wheel 83 is small in massand diameter to minimize the effect of flywheel action so that there isno danger of overshooting one tooth even though the movement of spring3.2 is very rapid. Furthermore, since only one tooth of ratchet wheel toprojects through the plate 22 in a posiion to be driven by the spring32, it is impossible for said spring to pass over the next tooth insequence and pick up a second tooth thereby advancing the clock at animproper rate. The tooth spacing of the ratchet wheel is intentionallysmaller than the travel of the end of spring 82 to insure that one-toothwill be fully advanced, but because of the manner in which the ratchetwheel is mounted in the plate said spring cannot pick up more than onetooth.

Very little energy is required for this drive but it is noteworthy thatall of the energy which is required either to move the ratchet, toovercome the restoring force of the springs 51, 58, or to overcomebearing friction, is supplied electrically through a force path which iscompletely independent of the balance wheel and hairspring.Consequently, the balance wheel is perfectly free to swing under theinfluence of the hairspring and an order of accuracy may be achievedwhich is far beyond that of good spring clocks and D. C. electricalclocks of the usual type.

To limit the range of rocking movement of the armature assembly ineither direction resilient bumpers are used. The latter are shown inFig. 2 to include a pair of oppositely extending leaf springs 35, 86having cup-shaped receptaclesat their ends for receiving small rubberblocks 81, 88. It has been found that this arrangement is not only quietbut also long wearing, absorbing little energy from the system.

If desired, means may be provided for imparting an initial manualimpulse to the balance wheel in order to put the clock into operation.Conveniently this is taken care of by means of a spring wiper 95 whichis mounted for rotation on a manually twistable shaft 9| so that thelower resilient portion 92 thereof comes into wiping engagement with theshaft of the balance wheel (see Fig. 2). A return spring 93 insures thatafter the manual twisting force, is released essence the wiper willreturn to an at-rest position well clear of the balance wheel shaft.Adjustment of the periodicity is effected in the present construction bymeans of an adjustable arm as which .is rotatable about the axis of thehairspring t3 and which has a slot 95 formed therein which engages theouter convolution of the hairspring. By thisarrangement the convolutionis allowed to move tangentially as required for the operation of thecontacts 15, Ma. However, at the extremes of the radial contraction andexpansion of the spiral spring, the outer convolution is brought againstone or the other of the walls of the slot 95 considerably shortening thelength of the hairspring during at least a portion of the cycle. Thedegree of such shortening may be varied with a Vernier-like action bymovement of the arm 91!. into an adjusted position to the right or tothe left of that shown. This adjusting arrangement does not subtract anyappreciable amount of energy from the hairspring 68 since the hairspringis freely floating in the central portion of the slot 95 during the timethat the tangential switch-operating movement is taking place.

Although the electrical connections between the contacts 15, 14a and thecoil it have already been referred to, they are set forth schematicallyin Fig. 12. The dual function of the return springs 51, 58 is wellbrought out. The arcing at the contacts will normally be very minor inview of the small amount of electrical energy which need be suppliedfrom the current source. If desired, however, the arcing which may talzeplace when the contact is broken may be considerably reduced by aresistor 96 placed across the terminals of the coil it. The value ofsuch resistor is not critical and may readily be determined by oneskilled in the art. The voltage surge which tends to occur when contactis broken is further reduced in the construction by means of theshort-circuiting copper sleeve id which forms a lag coil preventing anysudden change in the amount of flux threading the magnetic circuit. Thelag effect on the speed of the magnet has been found to be negligible.Tests conducted using the wide range of voltage have demonstratedclearly that the armature of movement is satisfactorily fast usingvoltages which are up to two volts greater or less than the six voltnominal rating. The fact that the mechanism can tolerate such a widerange variation without any sacrifice whatsoever in accuracy makes itpossible to use the clock even where the drain on the storage battery orother current source may vary over wide limits. In

this connection it is important to note that this feature enables theclock to be powered by dry cells which may suiier a considerable drop involtage before they are exhausted.

It will be seen that I have produced a clock which is not only of highinherent accuracy under all normally encountered operating conditions,but which is compact and eminently simple and straightforward ofconstruction. The only hearings in the entire clock which need haveminimum friction are those bearings which support the balance wheel. Theclock may be thus very cheaply constructed providing considerablecomvmercial advantage in a highly competitive field.

I claim as my invention: 1. In an electrical impulse clock an electro--magnet having a c-shaped pole piece, a springreturned armature assemblymounted within said ,pole piece, said armature assemblycomprising afirst mounting plate and a second mounting plate, means for holding saidplates in spaced relation, a magnetic armature rigidly mountedtherebetween, means for pivoting said armature assembly for balancedrotation about a central axis perpendicular to said plates, a balancewheel between said plates having bearings for allowing rotation about anaxis coincident with the central axis of said assembly, a hairspringadjacent said balance wheel and having its inner end coupled thereto, apair of electrical contacts one of which is arranged for movement by theouter end of said hairspring and the other of which is attached to oneof said mounting plates, means for insulating said mounting plates fromone another and a pair of hairsprings respectively associated with saidmounting plates for not only returning said armature assembly to adeenergized position but also for bringing out connections from saidelectrical contacts, said contacts being so arranged that closure takesplace upon rotation of aid balance wheel in a direction corresponding tothe rotation of said armature assembly into the deenergized position toeffect timed cyclical oscillation of said armature assembly.

2. In an electrical impulse clock an electromagnet having a pole piece,a spring-returned armature assembly cooperating with said pole piece,said armature assembly comprising a first mounting plate and a magneticarmature plate, means for holding said plates in spaced relation, meansfor pivoting said armature assembly for balanced rotation about acentral axis perpendicular to said plates, a balance wheel adjacent saidmagnetic armature plate having bearings for allowing rotation about anaxis coincident with the central axis of said assembly, a hairspringassociated with said balance wheel and having its inner end coupledthereto, a pair of electrical contacts one of which is arranged formovement by the outer end of said hairspring and the other of which isattached to one of said plates, means for insulating said plates fromone another and a pair of hairsprings respectively associated with saidplates for not only returning said armature assembly to a deenergizedposition but also for bringing out connections from said electricalcontacts, said contacts being so arranged that momentary closure takesplace upon rotation of said balance wheel in a direction correspondingto the rotation of said armature assembly into the deenergized positionto eiiect timed cyclical oscillation of said armature assembly.

3. In an electrical impulse clock an electromagnet having a pole piece,an armature assembly co-operating with said pole piece, said armatureassembly comprising a first mounting plate and a magnetic armatureplate, means for supporting said plates in spaced relation, means forpivoting said armature assembly for balanced rotation about a centralaxis, a balance wheel adjacent said magnetic armature plate havingbearings for allowing rotation about an axis 00- incident with thecentral axis of said armature assembly, a hairspring associated withsaid balance wheel and having its inner end coupled thereto, a pair ofelectrical contacts one of which is arranged for movement by saidhairspring and the other of which is attached to one of said plates,means for insulating said plates from one another and a springassociated with said armature assembly for returning said armatureassembly to a deenergized position, said contacts being so arranged thatclosure takes place upon rotation of said balance wheel in a directioncorresponding to the rotation of said armature assembly into thedeenergization position to energize said electromagnet and effect timedcyclical oscillation of said armature assembly.

4. In an electrical impulse clock an electromagnet having a pole piece,an armature assembly co-operating with said pole piece, said armatureassembly comprising a first mounting plate and a second mounting plate,means for holding said plates in spaced relation, a magnetic armaturerigidly mounted therebetween, means for pivoting said armature assemblyfor balanced rotation about a central axis perpendicular to said plates,a balance wheel between said plates having bearings for allowingrotation about an axis coincident with the central axis of saidassembly, a hairspring adjacent said balance wheel and having one endcoupled thereto, a pair of electrical contacts connected in circuit withsaid electromagnet, one of said contacts being arranged for movement bysaid hairspring and REFERENCES CITED The following references are ofrecord in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,772,556 Poole Aug. 12, 19302,420,827 Kennedy May 20, 1947 FOREIGN PATENTS Number Country Date188,079 Switzerland Mar. 1, 1937 682,134 Germany Oct. 9, 1939

